Divers have reported seeing the fuselage and engines of the crashed Lion Air jet on the seafloor and a ping locator has detected a signal that may be from the cockpit voice recorder, Indonesia's search and rescue chief has said.

Speaking on the sixth day of the search, Muhammad Syaugi said two engines and more landing gear had been found.

"I haven't seen it myself but I got information from some divers that they have seen the fuselage," Syaugi told a news conference at a Jakarta port on Saturday where body bags, debris and passenger belongings are first taken.

"We have heard a weak 'ping'," Syaugi said, which could be the cockpit's recorder. "The divers are still searching for it."